The present invention relates generally to high power magnetron oscillators and more particularly, to improved magnetron oscillators that are tuned using plasmas, and frequency tuning methods for use with magnetron oscillators.
High-power magnetrons are efficient generators of microwave power. They convert the kinetic energy from an electron beam into microwave- or millimeter-wave energy within a resonant cavity. The oscillation frequency is determined by the cavity, electron-beam voltage and current, and the externally applied magnetic field.
The high efficiency of magnetrons make them an attractive RF source for use in many applications; CW magnetrons have demonstrated efficiencies in excess of 80%. As an oscillator, however, the magnetron is inherently a narrowband device. While mechanically-tuned magnetrons are available, they suffer from several drawbacks. The maximum tuning rate is limited by the inertia of the tuning mechanism, whose moving parts penetrate the vacuum envelope of the magnetron, thus reducing the reliability of the magnetron.
The oscillation frequency of a tunable magnetron is varied by changing the resonant frequency of its resonant structure. In a mechanically-tuned magnetron this is achieved by mechanically altering the geometry of the resonant structure. This involves mechanically changing the dimensions of the cavity, with corresponding changes to beam voltage and magnetic field as needed, which changes the oscillation frequency of the magnetron. Mechanical tuning is relatively slow and requires a movable vacuum element so that the high-vacuum integrity of the tube can be maintained.
Accordingly, it is an objective of the present invention to provide for improved magnetron oscillators that may be rapidly tuned. It is another objective of the present invention to provide for improved magnetron oscillators that are tuned using plasmas. It is a further objective of the present invention to provide for frequency turning methods for use with magnetron oscillators.